1. Field of the Invention
The present invention relates to a system and method for extending RPR traffic management concepts to individual client flows while adhering to the station level traffic management functions described in the 802.17 specification by using a two tiered shaper approach.
2. Description of the Related Art
Resilient Packet Ring (RPR), specified in IEEE standard 802.17, is a standard designed for the optimized transport of data traffic over fiber rings. It is designed to provide the resilience found in SONET/SDH networks (50 ms protection), but instead of setting up circuit oriented connections, it provides a packet-based transmission. This is to increase the efficiency of Ethernet and IP services.
RPR works on a concept of dual counter rotating rings called ringlets. These ringlets are setup by creating RPR stations at nodes where traffic is supposed to drop, per flow (a flow is the ingress and egress of data traffic). Each ring segment used to transport data between stations is referred to as a span. RPR uses MAC (Media Access Control protocol) messages to direct the traffic, which traverses both directions around the ringlet. The nodes also negotiate for bandwidth among themselves using fairness algorithms, avoiding congestion and failed spans. The avoidance of failed spans is accomplished by using one of two techniques known as “steering” and “wrapping”. Under steering if a node or span is broken all nodes are notified of a topology change and they reroute their traffic. In wrapping the traffic is looped back at the last node prior to the break and routed to the destination station.
IEEE Standard 802.17 specifies RPR station level traffic shapers to control access to and dynamic sharing of available ring bandwidth. However, for systems that require the merging of multiple independent clients, each with individual traffic contracts, into a single RPR station, the need arises to add traffic management functionality at the client level. While doing so, strict adherence to the station level traffic management functions must still be maintained to be compliant with the ring level operation described in the 802.17 specification. A need arises for a technique by which the RPR traffic management concepts may be extended to individual client flows that adhere to the station level traffic management functions described in the 802.17 specification.